//
// Created by zhu on 25-8-31.
//
#include <iostream>
#include "Sales_item.h"

int main() {
    Sales_item item1, item2;
    std::cin >> item1 >> item2;
    // first check that item1 and item2 represent the same book
    if (item1.isbn() == item2.isbn()) {
        std::cout << item1 + item2 << std::endl;
        return 0; // indicate success
    } else {
        std::cerr << "Data must refer to same ISBN"
                << std::endl;
        return -1; // indicate failure
    }
}
